1. Technical Field
The present invention relates to pattern recognition, more specifically to arrangements for storing pattern data in memory in network workstations for use in detecting prescribed patterns in data streams.
2. Description of the Related Art
Workstation computers are currently being designed to include power saving mechanisms, where the workstation computer will shut itself down after a prescribed interval of inactivity.
One proposal for a power saving mechanism specifies a wake-up routine for the workstation computer, where a network interface to a network such as an Ethernet-type or IEEE 802.3 network maintains power to receive data packets from a network. Upon receiving a data packet having a prescribed pattern, the network interface causes the workstation computer to "wake up," for example to perform a prescribed operation requested by a remote workstation.
A problem encountered in implementing this type of wake up scheme is that the network interface device needs to be able to recognize certain patterns of data. The patterns typically are composed of specific bytes within the received data packet that must match a prescribed pattern, and other data bytes that are irrelevant to the pattern recognition and thus should be ignored. One possible solution is to store in memory a sequence of data bytes having a pattern identical to a received data packet, where a byte-by-byte comparison is made between the stored data and the received packet data. Such an arrangement, however, suffers from the disadvantage that additional overhead is necessary to enable the comparison hardware to distinguish the relevant bytes in the pattern comparison from the non-relevant (i.e., don't care) bytes stored in the memory. Moreover, since the received data packets may include a substantially large number of bytes that are ignored as don't care, the storage of null data in memory corresponding to bytes that are ignored in the received data packet results in a substantial waste of memory space.